The ability to rapidly switch between solutions of known concentration is a powerful tool for the study of ion channels and transporters. For outside-out patches where the diffusion path is short, the concentration can probably be changed in less than ten microseconds using an optimally designed solution switcher. Today's instruments can switch solutions in about 100 microseconds. The primary goal of this project is to design and construct a device that can switch solutions in less than 10 microseconds. The specific project goals are: 1. Construct a dual-stream laminar-low perfusion "mixer" by micro-machining silicon using photo-lithographic technologies. Demonstrate parallel flow between two exit streams with one micrometer separation. Current pulled theta glass devices have separations of 10 micrometers. 2. Rapidly move the mixer and exit streams over an isolated patch using a piezoelectric actuator with optimized mass, stiffness and steps size for this application. Demonstrate maximum velocities greater than 0.2 meters/second with minimum overshoot and ringing. 3. Maximize the rate of change at minimal flow velocity to preserve material and safeguard patch integrity. 4. Control the velocity of all streams, and the test solution concentration of one exit stream, via computer. 5. Explore using electro-osmosis to reduce thickness of the unstirred layer. PROPOSED COMMERCIAL APPLICATION: Burleigh's market experience indicates that at least 250 of the 2500 electrophysiology laboratories worldwide can potentially benefit from this new capability. Burleigh currently sells the LSS-3100 and LSS-3200 piezoelectric positioning system for Fast Solution Switching applications at the rate of 30 to 40 systems per year. Each system is 7,000 dollars for positioning capability only. This new technology adds significantly more value to Burleigh's product by incorporating the mixer and computer controlled pumps. We believe that this new product could be sold in quantities of 60 to 80 per year for a price of 10,000 to 12,000 dollars.